In this R01 renewal application, we propose to continue our work examining the role of T cell function in the control of acute and chronic HIV infection, for the purpose of developing meaningful correlates of protection in HIV infection that can be applied to HIV vaccine development. Here we will focus on the regulation of CD8+ T effector cell and CD4+ T helper type-1 cell function,by the transcription factors T-bet and eomesodermin (eomes), in order to understand the failings of the HIV-specific T cell immune response during acute and chronic HIV infection. We will further study the ability of different vaccine and adjuvant strategies to stimulate the expression of these key transcription factors. Previously we have shown that in chronic HIV infection, low expression of T-bet within HIV-specific CD8+ T cells is associated with poor effector CD8+ T cell responses and a failure to control HIV viremia. Our preliminary data demonstrates that although a massive (40-75% of T cells) acute effector CD8+ T cell response is raised during acute HIV infection, these responses cannot be maintained, perhaps due to their failure to upregulate and properly localize T-bet or eomes within responding cells, ultimately resulting in failure to control viremia. During this sam period, T-bet expressing HIV-specific CD4+ T cells are lost within weeks of infection, suggesting a rapid loss of T helper type 1 responses critical for the generation and maintenance of effective CD8+ T cell responses and antibody responses. Importantly however, T-bet expression is maintained in both HIV-specific CD4+ and CD8+ T cells in HIV elite controllers, suggesting that these responses play a key role in effective HIV-specific immune responses. Based upon these premises, we hypothesize a successful HIV vaccine will require stimulation of T-bet/eomes dependent HIV-specific CD8 effector and CD4 Th1 responses in order to mediate clearance or control of initial viremia. In this application we will therefore focus on defining effector CD8+ ad CD4 Th1 T cell responses in the control of HIV viremia, the transcriptional regulation of these responses, and whether these types of responses can be induced by different vaccine/adjuvant strategies. In Aim 1 we will define the relationship between CD8+ T cell effector function and T-bet/eomes expression and localization in HIV acute, chronic, and nonprogressive infection and how they relate to long-term control of viremia. In Aim 2, we will define the induction and maintenance of T-bet/eomes expressing CD4+ Th1 T cells in acute, chronic, and nonprogressive infection, and how these directly relate to the quality of the HIV-specific CD8+ T cell response and maintenance of CD8+ T cell effector function. Finally, in Aim 3, we will define the potential for T-bet and eomes to be modulated within human and rhesus macaque CD4+ and CD8+ T cells by current HIV vaccine and adjuvant strategies for application to both prophylactic and therapeutic (cure-based) HIV vaccine development.